Three of the following criteria have contributed to the recognition of Western Ghats, Sri-Lanka and Indo-Burma regions as hotspots of bio-diversity.
1. Species richness
2. Vegetation density
3. Endemism
4. Ethno-botanical importance
5. Threat perception
6. Adaptation of flora and fauna to warm arid humid conditions.

Which three of the above are correct criteria in this context?
A. 2, 4 and 6
B. 1, 2 and 6
C. 1, 3 and 5
D. 3, 4 and 6